Athenian democracy was a system in which the whole citizens of Athens were allowed to participate in government, making decisions for the whole city. Roman republic, on the other hand, was a government system dominated by the wealthy elites.
Compared to the Athenian democracy, Roman republic's political power was concentrated among a select few, rather than having the entire population as part of the decision-making process. Therefore, Athenian democracy influenced our current government more than Roman republic, as our democracy is based on similar principles of equal participation.